Heat Transfer Characteristics of the Non-uniform Grooved Tube considering Tube Expansion

A plate-fin heat exchanger is a type of heat exchanger widely used in air conditioners, and tubes and fins are tightly assembled by the mechanical expansion process of tubes. The tube expansion process deforms the grooves inside the tube, and the groove shapes also affect the adhesion between tubes and fins. In this study, the adhesion and heat transfer performance affected by the tube expansion of the non-uniform grooved tube with different heights are investigated by both analysis and experiments. From the analysis method, it was shown that the contact pressure of non-uniform grooved tube is higher than that of the uniform grooved tube, and the most appropriate high groove number of the non-uniform grooved tube is designed for the maximum contact pressure. From the experimental results, the decreasing rate of the condensation heat transfer coefficient is smaller in the non-uniform grooved tube with different heights, compared to the conventional uniform grooved tube. Also, the air side heat transfer coefficient of the non-uniform grooved tube with different heights is higher than that of the uniform grooved tube.